Yours are the second broken springs today. The first were on a Citroen C3. It's due to corrosion at the bottom because the springs are not made to resist this. Same applies to all European made coil springs in virtually all makes and models of European cars. To resist corrosion at the ends, springs need to be 'pigtailed', if they don't go round a strut, or tapered or flattened if they do. The cups that hold the springs at the bottoms of struts usually harbour salty road dirt. They are usually finished off by speed humps.